Urea rejuvenation of catalysts

Abstract

A spent catalyst comprising a zeolite base and an active metal such as a Group VIII noble metal is rejuvenated by contacting the catalyst with an aqueous solution containing urea.

What is claimed is: 
     
       1. A process for the rejuvenation of a spent hydrocracking catalyst from a hydrocracking process, said hydrocracking catalyst comprising a base-unstable crystalline zeolitic aluminosilicate and a Group VIII noble metal hydrogenation component, which process comprises contacting said spent hydrocracking catalyst with an aqueous solution containing urea at a pH from about 5 to 9.5 and at a temperature high enough for the rejuvenation reaction to proceed wherein said temperature is between about 70° C. and about 100° C. 
     
     
       2. The process of claim 1 wherein said aqueous solution contains urea, and one or more members from the group consisting of ammonium hydroxide and ammonium salts. 
     
     
       3. The process of claim 1 wherein said aqueous solution contains urea and nitric acid. 
     
     
       4. The process of claim 1 wherein said crystalline zeolitic aluminosilicate has a SiO 2  /Al 2  O 3  molar ratio of from 4.6 to 5.4, a face-centered cubic unit cell having an a o  of greater than 24.45 to 24.55 Å, an Na 2  O/Al 2  O 3  molar ratio of not greater than 0.25, an adsorptive capacity in the dehydrated state for oxygen of at least 26 weight-percent at 100 mm Hg oxygen pressure and -183° C., an ion-exchange capacity of from 0.15 to 0.35, and having the essential X-ray powder diffraction pattern of zeolite Y with the proviso that the d-spacing thereof having the Miller Indices 331 is at least as great in intensity as the d-spacing thereof having the Miller Indices 533. 
     
     
       5. The process of claim 4 wherein the pH of said aqueous solution is from about 8 to 9.5. 
     
     
       6. The process of claim 1 wherein said crystalline zeolitic aluminosilicate is a zeolite Type Y. 
     
     
       7. The process of claim 1 wherein said crystalline zeolitic aluminosilicate is made by the process which comprises; (a) providing a zeolite type Y having a SiO 2  /Al 2  O 3  molar ratio of between about 3.6 and 6, (b) contacting said zeolite Type Y with an aqueous solution containing sufficient ammonium cations for the ion-exchange to provide a M 2  O/Al 2  O 3  molar ratio of less than 0.15 where M is an alkali metal cation, and (c) thereafter contacting said zeolite Type Y with an aqueous solution containing sufficient magnesium cations for ion-exchange so that at least 25 percent of the aluminum atoms become associated with said magnesium cations. 
     
     
       8. The process of claim 1 wherein the said crystalline zeolitic aluminosilicate is made by a process which comprises; (a) providing a sodium zeolite Type Y having a SiO 2  /Al 2  O 3  molar ratio of about 4.8 (b) exchange said sodium zeolite Type Y with ammonium cations to a degree of about 85 equivalent percent, and (c) back-exchanging the product of step (b) with about 40 equivalent percent magnesium cations. 
     
     
       9. The process of claim 1 wherein the temperature is between about 80° C. and about 100° C. 
     
     
       10. A process for the rejuvenation of a spent hydrocracking catalyst said hydrocracking catalyst comprising a base-unstable crystalline zeolitic aluminosilicate and a Group VIII noble metal hydrogenation component, which comprises: (a) regenerate said spent hydrocracking catalyst under an oxidative regeneration to burn coke deposits;   (b) contacting said regenerated hydrocracking catalyst of part (a) with an aqueous solution containing urea at a pH from about 5 to 9.5 and a temperature between about 70° C. and about 100° C.